1. Field of the Invention
The invention relates to a plane discharge scheme AC type plasma display panel, and more particularly, to a cell structure of a plasma display panel for adjusting white balance.
2. Described of the Related Art
Recent years, a plasma display panel (referred to xe2x80x9cPDPxe2x80x9d hereinafter) of a plane discharge scheme AC type as an oversize and slim display for color screen has been received attention, which is becoming widely available.
FIG. 18 is a perspective view illustrating a configuration of a conventional AC type PDP when a front glass substrate 1 is separated from a back glass substrate 4.
In FIG. 18, a plurality of row electrode pairs (Xxe2x80x2, Yxe2x80x2) is arranged on the backside of the front glass substrate 1 and covered with a transparent dielectric layer 2 on a backside of which a transparent protective layer 3 made of MgO is formed.
The row electrodes Xxe2x80x2 and Yxe2x80x2 are respectively comprised of wider transparent electrodes Xaxe2x80x2 and Yaxe2x80x2 each of which is formed of a transparent conductive film made of ITO (Indium Tin Oxide) or the like, and narrower bus electrodes Xbxe2x80x2 and Ybxe2x80x2 each of which is formed of a metal film, complementary to conductivity of the transparent electrode. The row electrodes Xxe2x80x2 and Yxe2x80x2 are provided with respective projections Xaxe2x80x3 and Yaxe2x80x3 which are formed opposite to each other spaced at regular intervals, and alternating in the column direction such that the projections Xaxe2x80x3 and Yaxe2x80x3 oppose each other with a discharge gap gxe2x80x2 in between.
Each row electrode pair (Xxe2x80x2, Yxe2x80x2) forms a display line (row) of matrix display.
A plurality of column electrodes Dxe2x80x2 is arranged on the display surface side of the back glass substrate 4 to extend in a direction perpendicular to the row electrode pair (Xxe2x80x2, Yxe2x80x2). A band-shaped partition wall 5 is interposed each between the column electrodes Dxe2x80x2 to extend in parallel to other partition walls 5. And also, phosphor layers 6R, 6G and 6B in red (R), green (G) and blue (B), respectively, which comprise the three primary colors, are formed in order in the column direction to overlay side faces of the partition walls 5 and the column electrode Dxe2x80x2.
The front glass substrate 1 and the back glass substrate 4 having the above configuration are disposed in parallel and opposite to each other with an interposition of a discharge space. A discharge gas of a mixture of neon and xenon or the like is filled hermetically between the front glass substrate 1 and the back glass substrate 4.
In this manner, in each display line L, the discharge space is defined by the partition walls 5 at intersections of the column electrodes Dxe2x80x2 and the row electrode pair (Xxe2x80x2, Yxe2x80x2). This results in defining each discharge cell which serves as a unit light emitting area as described below.
An image is formed in the above AC type PDP as follows.
First, through address operation, the discharge is produced selectively between the row electrode pair (Xxe2x80x2, Yxe2x80x2) and the column electrodes Dxe2x80x2 in the discharge cells respectively formed with the phosphor layers 6R, 6G and 6B, to scatter lighted cells (the discharge cells are formed with wall charge on the dielectric layer 2) and nonlighted cells (the discharge cells are not formed with wall charge on the dielectric layer 2), over the panel in response to an image to be displayed.
After the address operation, in all the display lines L, the discharge sustain pulse is applied alternately to the row electrode pairs (Xxe2x80x2, Yxe2x80x2) in unison, and thus the plane discharge is produced in the lighted cells on every application of the discharge sustain pulse.
In this manner, the plane discharge in each lighted cell generates ultraviolet light, to excite the phosphor layers 6R and/or 6G and/or 6B formed in the lighted cell to emit light, resulting in displaying the image.
The aforementioned AC type PDP has outstanding properties to reduce thickness of a display and provide a color screen display with a high quality image.
In the conventional AC type PDP as explained above, the phosphor layers 6R, 6G and 6B formed in the respective discharge cells for displaying the three primary colors of red (R), green (G) and blue (B), differs in brightness of emission from one another. Therefore, if the discharge is produced in the discharge cells of respective colors having an equal emission area at the same number of times of the discharge, the display of a white color is difficult.
Therefore, conventionally, white balance (chromaticity of a white color) is adjusted by balancing the luminance of the three primary colors while the number of times of the discharge in each discharge cell is adjusted for each color on the phosphor layer.
However, the conventional method of adjusting the white balance as explained above has disadvantages in which a display gradation varies in each color, and also the number of display gradation levels itself is impaired. In addition, adjusting a display gradation of green having the largest influence over the luminance on screen, causes a disadvantage of reduction in the peak luminance on screen.
For example, if the number of times of the discharge in the discharge cells respectively formed with the phosphor layers 6R and 6G is reduced with respect to the number of times of the discharge in the discharge cell formed with the phosphor layer 6B, the discharge cell of the phosphor layer 6B can display up to 256 gradation level of the maximum luminance, but the emission luminance in the discharge cells of the phosphor layers 6R and 6G is achieved only by gradations lower than 256 gradation level.
As described above, if the adjustment of white balance is performed by adjusting the number of times of the discharge in each discharge cell for each color of the phosphor layer, the display gradations caused by light emission in the discharge cell vary for each color of red, green and blue, resulting in impairment of quality of gradation display.
The present invention has been made to solve the above problems associated with adjustment of white balance in the conventional AC type PDP as described above.
It is therefore an object of the present invention to provide a Plasma display panel which is capable of appropriately adjusting white balance without reducing each gradation level of the three primary colors of red, green and blue.
To attain the above object, a plasma display panel according to a first invention comprises a plurality of row electrode Pairs extending on a backside of a front substrate in a row direction and arranged thereon in a column direction to form display lines; a plurality of column electrodes extending in the column direction and arranged in the row direction on a face of a back substrate which opposites to the front substrate with interposing a space and constituting a discharge cell at each intersecting position with the row electrode pair in the space formed by the back substrate and the front substrate; and phosphor layers of the three primary colors of red, green and blue, respectively, which are respectively formed in a plurality of the resulting discharge cells in order, which is characterized in that the discharge cell formed with the red phosphor layer, the discharge cell formed with the green phosphor layer and the discharge cell formed with the blue phosphor layer, have a different opening area, opened toward the front substrate, from one another in accordance with each luminance of red, green and blue colors.
The plasma display panel according to the first invention is set such that an area ratio among the opening areas of the respective discharge cells relates with a predetermined relative ratio of luminance of blue, green and red.
According to the first invention, it is possible to adjust a relative emission luminance among the discharge cells during light emission by the plane discharge required for adjustment of white balance, only through controlling the opening area ratio among the discharge cells.
In consequence, as compared with the conventional method of adjusting the number of times of the discharge to the phosphor layer of each color for adjustment of white balance, since the discharge cell having a higher luminance of the phosphor layer is used as the reference, it is not required to increase the number of times of the discharge in the discharge cell having a lower luminance of the phosphor layer, so that the discharge current is not increased for the adjustment of white balance.
In the other way, since the discharge cell having a lower luminance of the phosphor layer is used as the reference, it is not required to decrease the number of times of the discharge in the discharge cell having a higher luminance of the phosphor layer, so that there may be no reduction in luminance on the screen in associated with the adjustment of white balance.
Since the display gradation of each color of the three primary colors becomes stable, the display gradation levels cannot be impaired, resulting in improvement in quality of display screen.
Moreover, since signal conditioning is not needed to adjust the number of times of the discharge in each discharge cell, the driving circuit configuration of PDP can be simple.
To attain the aforementioned object, the plasma display panel according to a second invention, in addition to the configuration of the first invention, is characterized by a part it ion wall including vertical wall port ions arranged between the front substrate and the back substrate to extend in the column direction and transverse wall portions arranged between the front substrate and the back substrate to extend in the row direction, to partition the space between the front substrate and the back substrate into the discharge cells in the row direction and the column direction, in which each of the transverse wall portions of the partition wall defining the discharge cell formed with the red phosphor layer, the discharge cell formed with the green phosphor layer and the discharge cell formed with the blue phosphor layer is varied in width in the column direction in accordance with each luminance of red, green and blue colors, to set the opening area of a front face of the each discharge cell opposing the front substrate.
The plasma display panel according to the second invention is set such that the discharge cells is partitioned by the rectangle shaped partition wall located between the front substrate and the back substrate, and each of the traverse walls of the partition wall partitioning the discharge cells in the column direction has a width in the column direction in accordance with luminance of the color of the phosphor layer in the discharge cell partitioned by the transverse walls. For this reason, each opening area of the discharge cells opening toward the front substrate relates to a predetermined relative luminance ratio among red, green and blue.
Hence, it is possible to provide a plasma display panel capable of properly adjusting white balance without reducing each gradation level of the three primary colors of red, green and blue.
To attain the aforementioned object, the plasma display panel according to a third invention, in addition to the configuration of the second invention, is characterized by comprising a dielectric layer formed on a backside of the front substrate to overlay the row electrode pairs, and formed with additional portions at portions thereof facing the transverse wall portions of the partition wall to jut out toward the transverse wall portions, wherein the additional portion is set to vary in width in the column direction in accordance with the width of the transverse wall portion of the partition wall facing the additional portion in the column direction.
In the plasma display panel according to the third invention, the additional portions formed in the dielectric layer to face the rectangle shaped partition wall and the transverse walls of the partition wall, divide the space between the front substrate and the back substrate into the discharge cells for each color of the phosphor layers.
Each width of the transverse wall of the partition wall and the additional portion of the dielectric layer facing the transverse wall is set in the column direction in accordance with luminance of the colors of the phosphor layers in the divided discharge cells. This determines the opening area of the discharge cell opening toward the front substrate in accordance with a predetermined relative luminance ratio of the three primary colors of red, green and blue. In consequence, it is possible to properly adjust white balance without the reduction of each gradation level of the three primary colors of red, green and blue.
To attain the aforementioned object, the plasma display panel according to a fourth invention, in addition to the configuration of the first invention, is characterized by including band-shaped partition walls located between the front substrate and the back substrate to extend in the column direction and be arranged in parallel in the row direction for partition of the discharge cells, in which any one of the partition walls is set to have a larger width than those of the remaining partition walls in the row direction to set the opening area of the each discharge cell on the side closer to the front substrate.
In the plasma display panel according to the fourth invention, the band shaped partition walls extending in the column direction partition the space between the front substrate and the back substrate into the discharge cells. At least one of the band shaped partition walls has a larger width in the row direction than those of the remaining partition walls to adjust an area ratio among the opening areas of the respective discharge cells in accordance with a predetermined luminance ratio among blue, green and red.
According to the fourth invention, it is possible to, only through controlling the opening area ratio among the discharge cells, perform the adjustment of a relative emission luminance among the discharge cells during light emission by the plane discharge which is required for adjustment of white balance.
In consequence, as compared with the conventional method of adjusting the number of times of the discharge to the phosphor layer of each color for adjustment of while balance, since the discharge cell having a higher luminance of the phosphor layer is used as the reference, it is not required to increase the number of times of the discharge in the discharge cell having a lower luminance of the phosphor layer, so that the discharge current is not increased for the adjustment of white balance.
In the other way, since the discharge cell having a lower luminance of the phosphor layer is used as the reference, it is not required to decrease the number of time discharge in the discharge cell having a higher luminance of the phosphor layer, so that there may be no reduction in luminance on the screen associated with the adjustment of white balance.
Since the display gradation of each color of the three primary colors becomes stable, the display gradation levels cannot be impaired, resulting in improvement of quality of display screen.
Moreover, since signal conditioning is not needed to adjust the number of times of the discharge in each discharge cell, the driving circuit configuration of PDP can be simple.
The plasma display panel according to a fifth invention is characterized by additional portions formed on positions of the dielectric layer facing the transverse wall portions to jut out toward the transverse wall portions not to form spaces between the additional portion and the transverse wall portions, and spaces are formed between the additional portion and the vertical wall portions of the partition wall.
According to the fifth invention, it is possible to prevent occurrence of improper discharge produced by interference between discharges of the discharge cells adjacent to each other in the column direction, resulting in high definition of screen.
The plasma display panel according to a sixth invention is characterized in that the phosphor layers are formed on side faces of the vertical wall port ions and the transverse wall portions of the partition wall and a front surface of the back substrate.
According to the sixth invention, the phosphor layer is formed on the five faces facing each discharge cell. This expands the surface area of the phosphor layers, or the light emitting area, as compared with conventional plasma display panels. Hence, with increase of luminance per discharge cell, it is possible to improve the luminance of the display screen much more than those of the conventional plasma display panels. In addition, as compared with the conventional plasma display panels, the luminance of the display screen is not decreased even if each discharge cell is reduced in size for enhancing definition of a screen.
The plasma display panel according to a seventh invention is characterized by a light absorption layer formed on a portion of the partition wall opposite to the front substrate.
According to the seventh invention, the light absorption layer formed on the partition wall absorbs ambient light incident from outside through the front substrate, to prevent reflection and improve contrast of the display screen.
The plasma display panel according to a eighth invention is characterized by a light absorption layer formed on a portion between bus electrodes of the row electrodes adjacent to each other in the two display lines.
According to the eighth invention, the light absorption layer formed between the bus electrodes of the row electrodes absorbs ambient light incident from outside through the front substrate, to prevent reflection and improve contrast of the display screen.
The plasma display panel according to a ninth invention is characterized in that each row electrode of the row electrode pair comprises a transparent electrode opposite to the other transparent with interposing a discharge gap in the each discharge cell, and a bus electrode connected to an end of the transparent electrode, locating distance from the discharge gap, in which the transparent electrode is formed in an independent island state in every discharge cell.
According to the ninth invention, since each transparent electrode constituting the row electrode pair is configured to be independent of the other transparent electrode in the island state in particular discharge cells, interference of discharges in the discharge cells adjacent to one another in the row direction may not occur even if the particular discharge cells are reduced in size for increasing the definition of the screen.
These and other objects and advantages of the present invention will become obvious to those skilled in the art upon review of the following description, the accompanying drawings and appended claims.